This invention relates to elevation-angle sensing instruments.
In celestial navigation, for example, a navigator traditionally has fixed his position on the earth's surface by using a marine-type sextant to measure the angles above the actual horizon of at least two celestial bodies, typically stars, planets, the sun, or the moon. Alternatively, the sextant was of the bubble type, which measures the angles relative to an artificially created horizon. Each measured angle, together with the time of its measurement, was used to ascertain a line of position using pre-calculated tables, a calculator, or a computer built into the sextant. Measuring the angle between the celestial body and the horizon and calculating position have been performed manually and, recently, electronically.
In surveying and construction, the measured angle between an artificially created horizon and an observed point (such as the top of a building or landmark) has been used to ascertain the elevation of the observed point.